When modeling, is there a way to have light shine from behind viewport camera?
You can put the scene lights on a separate layer, turn them of during viewport editing, and then parent a new lamp to the back of the camera. You can turn off the restrict rendering setting for the test lamp in the outliner. 

This works in Blender Internal, but not in Cycles. You could test texture placment in BI, and then render from Cycles. It's possible to create shaders that work cross-engine, you just have to add the specific outputs. The BSDF nodes wouldn't work in BI, but the textures would.